How would you do this???

I really don't like many knobs on a bass. I'm also not crazy about stacked knobs. How would one go about being able to control 7 variables with two knobs? Is there a system where someone could use 2 knobs in conjunction with two 2 or 3 way switches? One switch position allows you to adjust volume with one knob, another position allows you to blend pups with the same knob? Or, independently set bass, mids, treble? Another position allows you to set passive tone?

A blend pot and a volume pot are two different things. So, no, those two functions could not be mediated through a switch connected to a single pot.

The other problem is that the preamp has no "memory", so when you flip the switch, the function you were using the pot for (say, treble) goes flat again when you switch to the new one (say, bass). So, even though you have a 3 band EQ, if you go with one knob, you only get one EQ function at a time.

Instead of having variably control over all the parameters you could just make several different hard wired schemes and then switch between them. With two six-postion rotary <a href=" http://www.futurlec.com/SwRotary.shtml"> switches<a/> you could have 36 different settings.